No mas pantalones! Now we turn to a tragedy that will be discussed in so many families. A 100-year-old driver, schoolchildren hurt, and everyone wondering tonight, what should be done. Here's abc's nick watt. Reporter: Preston carter was backing up just as school was letting out. He mowed 11 people down, three 4-year-old boys among the seriously injured. I'm sorry. Reporter: The centenarian claims his brakes failed. An investigation is underway, but so far no charges. When a senior's behind the wheel, a crash makes news. An 83-year-old heading the wrong way on i-5 last year. A 70-year-old backing up over a police car after a ticket. Santa monica farmer's market, an 89-year-old driver killed 10, injured 70. But -- driving is a function of ability, not age. Reporter: But ability can diminish with age and infirmity. It shouldn't take an incident like this to provide a wake-up call. Reporter: A wake-up call about how old is too old to drive. If you think grandpa's a danger,

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